I've downloaded the relevant package files from the Brother support site and unpacked/installed them. CUPS 'sees' the printers, gets and claims to set the available options and sends both 'print test page' and 'print self test' print jobs which it claims go through to completion. However, nothing prints.

I've read all the relatively recent {2010 and newer} Brother printer related posts I could find in the Gentoo forums including:

At this point, I've read so much I'm dazed and confused rather then enlightened.

The following information may mean something to someone.

To get the information below, I reset the CUPS log files, restarted 'cupsd' {and associated 'cups-browserd'} and created two DCP-7065DN printers. One printer for each method of access 'seen' by CUPS. In each case, I pointed to the 'ppd' file I got from Brother's support site.

After creating each printer, I sent a 'print test page' and a 'print self test' for the newly created printer. These are the resultant printer creation, print jobs and associated logs:

Maybe the same will work for you. In sort, select a PPD driver for a similar printer model from the foomatic-db; these printer drivers are listed in the CUPS installation page. It appears that they are GPL'd printer drivers.

The one I selected was:
Brother MFC9840CDW Foomatic/Postscript

My connection string is "lpd://10.0.1.NNN/BINARY_P1" The IP address was mis-reported by the printer discovery mechanism.

I can't confirm that Brother printers suck...
Connecting via socket:// always worked for me. Of course you need to setup your router properly, so that you have a save range for static IPs in order to prevent DHCP occupying the IP of your printer.
And just last week I got my third Brother printer (MFC 7360N), and all of them just worked as they should. I am using the drivers provided by Brother.

franzf: I'm glad you've had good experiences with this. However, my experiences with the MFC 9970CDW seem to indicate that this particular driver is just broken. I *did* try the socket:// interface as well, as well as ipp:// and http:// (I don't recall the exact strings at the moment). It seems that dufeu's experience with the DCP-7065DN is similar. ...but perhaps my commentary was a bit over-generalized, written in my fit of frustration. Many, many attempts were made, with a variety of seemingly-logical connection strings, on multiple platforms, 32- and 64-bit, with multiple distributions.

It was only after switching to the footmatic-db's MFC9840CDW driver that I could get our MFC 9970CDW to print.

With the drivers from Brother, I could print a test page, but could not print from any apps.